The goal of our research is to uncover the neuronal mechanisms that limit the development of visual performance in primates. Recent advances in visual psychophysics and theory have made it possible to formulate questions about visual development in the same terms used to study adult vision, and we propose experiments to explore the neurobiology of development in these functional terms. We plan studies of the basic visual functions of resolution and contrast detection, and of the higher-level functions of visual motion and pattern perception. To understand the development of visual resolution and contrast detection, we will quantitatively analyze the properties of V1 neurons in macaque monkeys at several developmental stages. We will compare neuronal performance to behavioral measurements, and compare both behavioral and neuronal performance with measurements of the mosaic of photoreceptors that sets the fundamental sampling limits to vision. We seek to test the hypothesis that neuronal performance in V1 sets the limits to development for basic visual capacities. To understand the development of visual pattern and motion perception, we will study the development of visual sensitivity to form and motion signals carried statistically by the distribution of dots in Glass patterns , created by pairing randomly placed dots with partners having particular spatial and temporal offsets. To detect these patterns, signals must be integrated across the stimulus array; because each dot is made clearly visible, peripheral limits to detection and resolution do not affect performance and central processes can be probed directly. To discover the cortical mechanisms that support the perception of form and motion, we will use identical stimuli to test the development of responses of neurons in V1, V2, V4, and MT. Statistical methods permit the direct comparison of neuronal and behavioral performance in terms of the efficiency with which these patterns are seen. To explore the anatomical basis for the development of the functions we have chosen, we will study the development of the intrinsic and extrinsic connections of these cortical areas, and compare these with changes in the distribution of several molecular markers that delineate cortical functional architecture. Taken together, our experiments will provide unified descriptions of the anatomical, physiological, and behavioral processes whose development determines much of adult visual function. These analyses will provide the foundation for exploring developmental abnormalities that affect vision and other functions of the cerebral cortex.